Extraction of liquid from liquidbearing material



Patented Sept. 21, 1954 EXTRACTION IOF LIQUID FROM LIQUID- BEARING MATERIAL Gordon Wilson MacIlwaine, Southwold, Brough, England N 0 Drawing. Application April 15, 1952, Serial No. 282,473

The present invention relates to an improved method for the extraction of solute from solute bearing material.

The invention will be further set forth in connection with the extraction of oil from vegetable matter such as seeds, but is generally applicable.

Whereas it has been the common practice to date to remove the contained oil from nuts, oil seeds and the like oil-containing vegetable matter, by pressure, either hydraulic or mechanical, on the one hand, either as single processes in themselves, or by one process followed by the other, or by an extraction process employing a volatile solvent, or by a combination of either or both of the former with the latter, these processes as practised-today are found to contain certain disadvantages.

In using the hydraulic system of pressing for the removal of oil, the main disadvantage is that this process is of a batch nature, requiring much handling, and the resultant press cake is of slab form, which must be broken down before being used for its primary purpose of animal feeding. In order to perform this hydraulic process as efficiently as possible, it is necessary to raise the temperature of the pre-rolled seed mass by a heating treatment, whether it be dry heat or open steam, in order to render the contained oil less viscous, so that during the pressing process this oil can be displaced more efficiently. Under most favourable conditions of temperature and pressure, a residual oil content remaining in the press cake of between 4-6% is generally regarded as economical.

Today oil is expressed by continuous methods in what are known as expellers, or screw presses, in which an interrupted Archimedean screw is provided as a means of carrying the oil-bearing material through the centre of a perforated memher.

The screw is arranged with a diminishing pitch, or other means are adopted to reduce the volume of the material being treated.

This volumetric reduction displaces oil contained in the mass, which escapes through the perforations in the member enclosing the screw.

These methods are an improvement on the hydraulic press because they require less labour, are continuous, and produce a cake which generally does not require further reductionin size before use.

They have the disadvantage, however, that they all use far more power than is necessary for attaining the sameresults with hydraulic presses.

8 Claims. (Cl. 260-4121!) The power consumption is proportionately greater when high pressures necessary for a low oil content in the finished cake are applied. This is because in a screw press or expeller increase in pressure is obtained by reduction in volume, and at high pressures the volume becomes nearly irreducible. curs and considerable energy is dissipated in heat,

If it is attempted to accomplish the: same results with a single expeller as are usually obtained with the hydraulic press, the rise in temperature is sufiicient to afiect adversely the quality of the oil, and to scorch the cake, and the wear and tear on working parts, and power consumption maybe abnormally high.

The process of extraction by the use of a volatile solvent as practised commercially for many years past is a vast improvement on any hydraulic or mechanical crushing process, when the yield of oil from any seed, nut or the like vegetable material is of prime importance, because, by the use of a volatile solvent, the residual oil, if the process is properly carried out, need never exceed 2% and may be as low as under The process of solvent extraction has been in the past, and still is, carried out as a batch process, though some continuous plants are in use today in which the material to he oil-freed is passed in counterflow to the solvent. In either case, however, the principle underlying the solvent extraction process involves the use of the requisite quantity of volatile solvent to ensure the displacement of the oil from the pre prepared mass to the point where this oil is taken into solution with the solvent, and can be removed from the extraction vessels as an oilsolvent mixture or miscella by either gravitation or inducement by pump or the like. The underlying principle is that of washing out the oil by the use of a large quantity of volatile solvent. Steps have been taken throughout the years to ensure that economical use has always been made of the solvent as a carrier, by ensuring that it is given every opportunity to pick basis, the main disadvantage of the solvent extraction or washing out process is the relatively large volume of miscella which is obtained and which must then be distilled in order to recover the solvent and oil as separate fractions.

Processes have been devised which employ two Under these conditions, slip 0c or even all three of these means of oil separation from seeds and the like, by the fact that the expeller is employed to remove the first "easy oil from the prepared mass, with a view to avoiding excessive power and wear, and the like, and then this mass, partially oil-freed, is passed to: the batch or continuous solvent-extraction process to complete oil removal, but in all cases again the wash principle has been adhered to.

An object of the present invention is to provide a method of extracting solute from asolutebearing material wherein an improved overall'extraction of solute is obtained whilst using less solvent than employed in conventional washing-. out processes.

According to the present invention, .a solvent is added to a solute-bearing solid from which solute is to be extracted, such as oil-bearing vegetable seeds, in quantity sufficient to saturate, or partly saturate the same, that is to say, equal to or less than the amount ofliquid solvent addition which would result in gravity draining or bleeding of the impregnated material, which material is then subjected to mechanical pressure so that some of the solution is squeezed out.

It will;be preierredthat the residue, which may still have an appreciable liquid content, is then again impregnated with solvent or miscella, that is to say, the expressed liquid, and again treated by mechanical pressure, this process being repeated one or more times until the liquid content occluded or bound up in the solid material has been reduced to a desired proportion.

For example, for a high recovery of solute, it would be desirable for solute-free, or substantially solute-free solvent to be used for impregnation of the solute and solvent containing material in the stage immediately before its final discharge.

The liquid squeezed from this final stage would be used for the impregnation for the stage next to the final stage with additions of solute-free, or substantially solute-free solvent, if necessary.

By this means, there would be a progressive increase in the solute content of the solution used for consecutive impregnations from the ma-,- terial discharge stage: to the stage where unextracted solute-bearing material is received, and conversely a decrease'in-the solute content-of the solid between the stage where it is initially treated to the stage at which it is discharged.

The number of stages will be varied according to the solute contentof the materialto be treated and the amount of. solute .it is considered desirable or economical to leave in the'extracted material.

Extraction of the solute is facilitated if the solute bearing material is subjectedtopulverisation prior to treatment with the solvent.

In certain tests taken upon palm-kernels and on rolled undecorticated ground nuts respectively of the following'analysis, the following results were obtained using commercial petrol as a solvent.

In these tests, for convenience, oil free commercial petrol at atmospheric temperature was added at each stage, but in commercial plant the expressed liquid could be employed as described in the foregoing.

1. An old sample of flaked palm kernel Oil percents; 41 Moisture i do 6.34 Oil (dry basis) do 44 Weight per cubic foot inv free condition. as

charged to the test cylinder lbs. 20.5

2. Rolled undecorticated groundnuts Oil percent 43.7 Moisture do 4.36 Oil (dry basis) do 45.6 Weight per cubic foot in free condition as charged to the test cylinder lbs. 18.3

Retention of solvents The following figures give the percent of liquid,

i. e. initial oil plus added solvent as a percentage of units by weight of wet solids.

Undecor Palm Kerticated nel Meal groundnuts A. Solvent added to meal in iunnel Percent Percent Petrol; 53. 59. 0 B. Solvent added to meal in a container and shakenPetrol 58 60.0

In a multiple pressing using a maximum pressure of 7150 'lbs. per sq. inch, the following results were obtained.

Solvent-.Wetted Meal Undecorti- Palm cated Kernel groundnuts Percent oil in meal- (before wetting) 41. 5 43. 7 1st Pressing:

Oil removed as percent oil available" 80. 5 79 Percent oil content of cake 11.5 13.1 Percent oil content of miscella 63. 5 58 2nd Pressing;

Oil removed as percent ofoil available. 93 92. 5 Percent oil content of cake 4. 25 5 Percent oil content of miscella 2l. 2 23. 5 3rd Pressing:

Oil removed as percent of oil available. 96. 8 98 Percent oil contentv of cake 2.04 2.1 Percent oil content of miscella 7. 6 7. 8 4th Pressing:

Oil removed as percent of oil available. 98. 6 99 Percent oil content of cake (wet basis). 0.8 0.6 Percent oil content of miscella 3.8 4. 1

In the foregoing, fresh solvent was added at the commencement of each pressing. Cake analysis is on wet basis. Percent of oil removed is cumulative value at each stage.

Solvent. to meal ratios- In the foregoing the-ratios of solvent to un-' extracted meal for each pressing were:

By weight Palm kernel 0.3? to Undecorticated groundnutssn 0.33 to 1 It should be noted that these ratios, with four pressings at about 7,1501p1 s. i. gave acake-with' about 1% of oil (wet basis).

By the present invention the steam consumption for driving ofi the solvent from the solute will be considerably less than -for a normal solvent extraction process, as much lesser quantities of solvent are nowusedj and further, the temperature of extraction can be kept low and need not rise substantially above atmospheric temperature, resulting in extraction of' oils from vegetable seeds, whale livers and similar oilbearing materials of much better quality and colour.

I claim:

1. A method of extracting oil from'oil bearing solid material selected from the groupconsisting ofrve'getable'seeds and" whole alivers comprising impregnating' the oil bearing solid ma-* terial with a solvent in quantity no greatenthan r the amount of solvent addition which would the impregnated seeds, and thereafter subjecting the solvent impregnated seeds to mechanical pressure to a degree suflicient to extrude therefrom oil taken up by the solvent.

3. A method of extracting oil from vegetable seeds consisting in impregnating the vegetable seeds with a solvent in quantity not greater than the amount of solvent addition which would just result in gravity draining of the impregnated seeds, subjecting the solvent impregnated seeds to mechanical pressure to a degree sufficient to extrude therefrom oil taken up by the solvent, re-impregnating the pressed seed mass with a further amount of solvent in quantity not greater than the amount of solvent addition which would just result in gravity draining of the impregnated seed mass, subjecting the solvent impregnated seed mass to mechanical pressure, and repeating the process until the amount of oil remaining in the seeds is reduced to a minimum.

4. A method of extracting oil from vegetable seeds as claimed in claim 3, in which the solvent used for impregnating the pressed seed mass consists of miscella.

5. A method of extracting oil from vegetable seeds selected from the group consisting of palm kernels and groundnuts consisting in impregnating the vegetable seeds with a hydrocarbon solvent in quantity no greater than the amount of solvent addition which would just result in gravity draining of the, impregnated material, and thereafter subjecting the solvent impregnated seed mass to mechanical pressure to a degree sufiicient to extrude therefrom oil taken up by the solvent, whilst maintaining the seed material throughoutthe extraction at a temperature which does not substantially exceed atmospheric temperature. l

6. A method of extracting oil from vegetable seeds consisting in first pulverising the vegetable seeds, impregnating the pulverised vegetable seeds with petrol in quantity such that the ratio of petrol to pulverised material does not exceed 0.4 to 1, thereafter subjecting the petrol impregnated seed mass to mechanical pressure to a degree sufiicient to extrude therefrom oil taken up by the petrol, ire-impregnating the pressed seed mass with a further amount of petrol in the same proportion of petrol to material as hereinbefore, thereafter subjecting the petrol impregnated seed mass to mechanical pressure,

and repeating the steps of re-impregnation followed by mechanical pressure using the proportion of petrol to material as hereinbefore defined until the amount of oil remaining in the seeds is reduced to a minimum.

7. A method of extracting oil from vegetable seeds as claimed in claim 6 in which petrol containing extracted oil is used as the extraction solvent at each stage excepting the last extraction prior to the discharge of spent seeds when oil free petrol is employed.

8. A method of extracting oil from vegetable seeds comprising pulverising the vegetable seeds, impregnating the pulverised vegetable seeds with a hydrocarbon solvent in quantity such that the ratio of solvent to pulverised seed material is of the order of 0.4 to 1, subjecting the solvent impregnated seed mass to mechanical pressure not exceeding 7150 lbs. per square inch, and collecting the oil extruded, re-impregnating the pressed seed mass with a further amount of hydrocarbon solvent in quantity such that the ratio of solvent to pressed seed mass is again of the order of l 0.4 to 1, subjecting the solvent impregnated mass to further mechanical pressure not exceeding 7150 lbs. per square inch and adding the oil extruded to that quantity previously extruded, and repeating twice more the steps of re-impregnation followed by mechanical pressure using the proportion of solvent to pressed seed mass and the degree of mechanical pressure as previously employed.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,158,427 Reichert May 16, 1936 2,183,837 Hamilton et a1 Dec. 19, 1939 2,253,696 Fauth Aug. 26, 1941 2,467,403 Pascal Apr, 19, 1949 FOREIGN PATENTS Number Country Date 196,484 Canada Jan. 2'7, 1920 

1. A METHOD OF EXTRACTING OIL FROM OIL BEARING SOLID MATERIAL SELECTED FROM THE GROUP CONSISTING OF VEGETABLE SEEDS AND WHOLE LIVERS COMPRISING IMPREGNATING THE OIL BEARING SOLID MATERIAL WITH A SOLVENT IN QUANTITY NO GREATER THAN THE AMOUNT OF SOLVENT ADDITION WHICH WOULD JUST RESULT IN GRAVITY DRAINING OF THE IMPREGNATED MATERIAL, AND THERAFTER SUBJECTING THE SOLVENT IMPREGNATED OIL BEARING MATERIAL TO MECHANICAL PRESSURE TO A DEGREE SUFFICIENT TO EXTRUDE FROM SAID MATERIAL OIL TAKEN UP BY THE SOLVENT. 